Filtrete 15"x20"x1" Red Micro Allergen Defense Pleated Furnace Air Filter. It is 90% effective at capturing large allergens like mold spores and pet dander. It is electrostatically charged to capture microscopic allergens like dust, smoke, and smog. It captures bacteria and particles that can carry viruses. It meets the guidelines of the American Lung Association Health House Program. It has a MPR rating of 1000 and lasts up to 3 months.